Summary A Beech 1900D aircraft, C-GLHO, serial number UE-266, operating as LabAir8333, was taxiing on Runway02/20 when the aircraft struck a two-foot-high windrow which lay across the runway just to the north of taxiway Charlie. There were no injuries to the 10passengers and two crew members. The aircraft sustained substantial damage. The accident occurred at 0844 Newfoundland standard time. Ce rapport est galement disponible en franais. Other Factual Information St. John's Airport is a certified, controlled airport. The airport has three runways - 11/29, 16/34, and 20/02, and all three runways are used throughout the year. Snow removal and winter runway maintenance priorities are established in the St.John's Airport Winter Maintenance plan. Because of its CategoryII instrument approach capability, and unless wind conditions clearly favour Runway16/34, snow clearing efforts are initially focussed on preparing Runway11 and the associated runways and taxiways that are necessary for access. The various airport surfaces are designated under one of three priorities for snow clearing (seeFigure1). Priority3 surfaces are cleared last. Runway02, north of taxiway Charlie to the entrance to taxiway Bravo, is designated as a priority3 surface when either Runway11/29 or 16/34is active. Figure1. Snow Clearing Priorities with Runway 11/29 Active The St. John's Airport Winter Maintenance plan also includes criteria for the closing of an active runway because of contamination. One of these criteria is that an active runway should be closed if there are windrows in excess of 12inches high. The plan, however, does not contain instructions for the closing of non-active runways such as the portion of Runway20/02 north of Charlie taxiway, or other low priority surfaces. Windrows in priority3 regions, such as the one north of taxiway Charlie, are not normally encountered by taxiing aircraft, and are not usually reported to the ground controller, nor indicated on the runway surface condition (RSC) reports. The normal practice at the airport is for snow removal crews to advise the ground controller of windrow hazards when they hear a taxi clearance, or a request for taxi, through an area with a windrow. Canadian Aviation Regulation CAR302.07 - Obligations of the Operator [Airport],(2)(b), requires that the airport operator provide the air traffic control unit with immediate notice of the existence of any obstruction or hazardous condition affecting aviation safety at the airport. The weather during the night before the accident was varied. Prior to 0530 Newfoundland standard time (NST)1, light snow had been falling, and the wind was from the east. Initial airfield maintenance activities were therefore focussed on clearing snow from Runway11 and the related taxiways. It could not be determined precisely when, or by whom, the windrow was created; however it is during this initial period that the windrow to the north of Charlie taxiway was created by plowing activities. By 0550, a 100-foot-wide centreline on Runway11/29 had been prepared, and the runway friction index was measured at.30, indicating generally good friction. By 0600, the snow had changed to ice pellets, and between 0600 and 0630, freezing drizzle started falling at the airport. Runway11 became ice covered, and, as a result, an Air Canada Airbus, Flight601, slid on the slippery runway surface while backtracking and was not able to stop before encountering the runway end. Flight601 radioed the tower at 0634, informing them that they were at the runway edge and were unable to manoeuver from that position. The night shift supervisor (lead-hand) and various airfield maintenance vehicles proceeded to Flight601's position. At 0640, the tower reported that the wind had shifted, and was now from 170degrees at 10to 15knots, clearly favouring Runway16. The lead-hand and the field maintenance crew were now preoccupied with two tasks: extricating Flight601, and preparing and inspecting Runway16 for use. By about 0755, Flight601 had been towed from its position at the runway end by a company tug and was then inspected by company maintenance personnel. At 0752, a weather special was released showing that the freezing drizzle had stopped, and the winds were now from the south at six knots. At 0757, the crew of the Beech1900D taxied the aircraft from apron two, via taxiway Charlie, Runway34, Runway20/02, and taxiway Foxtrot onto Apron1. Here, the aircraft was shut down and prepared for the upcoming Lab Air8333 flight. Around 0815, the day lead-hand proceeded onto the airfield to relieve the night lead-hand. Normally, one of the first actions of an oncoming lead-hand is to inspect the entire airfield by vehicle. However, in this instance, the oncoming lead-hand proceeded directly to Runway11/29 to meet with the night lead-hand and lend assistance with Flight601. The customary airfield survey was not completed. The wind had now shifted to 240magnetic at 10to 15knots, and it was decided to switch to Runway29. Airfield maintenance sanded the runway and the threshold of Runway29. The night lead-hand completed an inspection of Runway29, then departed the airfield at about 0822. Flight601 started engines, backtracked down Runway29, and was cleared for take-off from Runway29 at 0840. At 0841, Lab Air Flight 8333 was cleared to taxi via Foxtrot, Runway02, and to hold short of Runway29 (seeFigure2). An analysis of the flight data recorder (FDR) information showed that the aircraft was travelling at about eight knots and was accelerating when it rolled out on the runway, heading on Runway02. As the aircraft approached the intersection of runways02 and34 there were several snow removal vehicles on Runway34 east of the intersection. After confirming that the vehicles were holding short, the crew proceeded through the intersection, initiating the instruments portion of the taxi check nine seconds prior to striking the windrow. According to the operator's standard operating procedures for the instrument cross-check, the captain (pilot flying), must look inside the cockpit to call out indications from the aircraft's flight instruments. Meanwhile, the first officer (pilot not flying) is supposed to also monitor the instruments and when found correct will respond Checked and Set Left/Right. As the crew were conducting this check, the windrow was spotted. The aircraft was now 3.5seconds and 146feet2 from the windrow and travelling at 24knots. The captain attempted to stop with wheel braking, approximately two seconds later and 60feet short of the windrow. When the wheel brakes were applied, the aircraft started to skid on the slippery runway surface. The captain attempted to apply reverse thrust, but there was insufficient time for it to be selected before the nosewheel struck the windrow, at 23.5knots. The propellers struck the windrow next, followed one quarter of a second later by the main gear, which struck the windrow at approximately 20knots. The lowest point of the propeller tip path on the Beech1900D is 14.07inches from the ground. When the propeller blades struck the two-foot-high windrow, all four blades from the right engine and one blade from the left engine broke off near the hub. The blades from the right engine struck the starboard aircraft fuselage at the forward passenger cabin window. This window shattered and the window fragments and frame were thrown forcibly into the cabin. A mother and her infant, who were seated immediately next to the window, narrowly escaped injury. The crew stopped the aircraft 175feet past the windrow, secured the engines, shut off the electrical power, and escorted the passengers from the aircraft. The ground controller noticed the passengers deplaning and activated the crash alarm. The weather at the time of the accident was as follows: wind 230true at 10,gusting to 15,knots and visibility four statute miles in light drizzle and mist. Light conditions were described as being flat: there were no shadows thrown by objects on the ground. Runway 02, from Charlie taxiway to Runway29, had not been traversed by any vehicle prior to the accident. The runway had not been cleared during the previous night, and there were no RSC reports produced for the runway. As the location of the windrow north of Charlie taxiway was well to the north of Runway16/34, the windrow did not appear on any of the RSC reports produced that night. After the accident, Runway20/02 north of the windrow was found to be covered with a combination of ice and patches of thin snow. The aircraft was fitted with both a cockpit voice recorder (CVR) and an FDR. Both operated normally. The information from these units, as well as from air traffic control (ATC) and airport authority recordings, was useful in analysing events related to the accident. The aircraft emergency checklist contains a procedure for propeller collisions on the ground. The checklist states: Propeller Collisions during Ground Operation During collisions, the higher the propeller RPM, the greater the risk of propeller blades, or portions of the blades, separating from the propeller hub causing damage to the fuselage and physical harm to the passengers. If maximum braking and maximum reverse are insufficient, and a ground collision is imminent: Power Levers......GROUND FINE OR CUT OFF Condition Levers......FUEL CUTOFF